Fabrication of novel elastosomes for boosting the transdermal delivery of diacerein: statistical optimization, ex-vivo permeation, in-vivo skin deposition and pharmacokinetic assessment compared to oral formulation

Figures & data

Table 1. The independent variables, their respective levels, and the model summary statistics of 4¹.2¹ full factorial design used for optimization of DCN elastosomes.

Factors (independent variables)	Levels of variables
X1: type of EA X2: amount of EA (mg)	Brij S2 5		Brij C10		Cremophor EL	Cremophor RH 40 10
Responses (dependent variables)	R^2	Adjusted R^2	Predicted R^2	Constraints	p value	F value	Adequate precision
Y1: EE%	0.8109	0.6455	0.2438	Maximize	.0199	4.90	7.271
Y2: PS (nm)	0.9477	0.9019	0.7907	Minimize	.0002	20.70	12.468
Y3: PDI	0.5049	0.0718	−0.9802	Minimize	.4132	1.17	2.794
Y4: ZP (mV)	0.9644	0.9332	0.8576	Maximize (as absolute value)	<.0001	30.95	16.836
Y5: DI (g)	0.8309	0.6830	0.3236	Maximize	.0134	5.62	6.206

EE%: entrapment efficiency percentage; PS: particle size; PDI: polydispersity index; ZP: zeta potential; DI: deformability index.

Figure 1. Response 3D plots for the effect of type of EA (X₁) and amount of EA (X₂) on (A) entrapment efficiency percentage (EE%), (B) particle size (PS), (C) polydispersity index (PDI), (D) zeta potential (ZP), and (E) deformability index (DI) of DCN elastosomes.

Table 2. Experimental runs, independent variables, and measured responses of the 4¹.2¹ full factorial experimental design of DCN elastosomes compared to DCN-loaded bilosomes (A) and the observed and predicted values of the optimal elastosomes (E1) (B).

	X1: type of EA	X2: amount of EA (mg)	Y1 EE%^a	Y2 PS (nm)^a	Y3 PDI^a	Y4 ZP (mV)^a	Y5 DI (g)^a
(A) Formulations
E1	Brij S2	5	96.25 ± 2.19	506.35 ± 44.61	0.46 ± 0.09	−38.65 ± 0.91	12.74 ± 2.63
E2	Brij S2	10	91.50 ± 2.33	576.65 ± 53.38	0.74 ± 0.04	−40.60 ± 0.28	5.25 ± 3.15
E3	Brij C10	5	90.20 ± 0.28	611.50 ± 150.61	0.79 ± 0.14	−35.90 ± 0.42	9.28 ± 2.29
E4	Brij C10	10	87.00 ± 0.56	368.75 ± 3.46	0.40 ± 0.11	−38.75 ± 0.71	6.75 ± 1.06
E5	Cremophore EL	5	93.85 ± 2.33	796.75 ± 69.22	0.41 ± 0.13	−37.55 ± 3.39	40.75 ± 17.30
E6	Cremophor EL	10	90.89 ± 0.27	1000.95 ± 125.93	0.69 ± 0.01	−41.65 ± 0.21	14.50 ± 13.43
E7	Cremophor RH 40	5	94.05 ± 2.61	1087.00 ± 103.23	0.27 ± 0.09	−38.35 ± 0.21	9.65 ± 2.61
E8	Cremophor RH 40	10	91.50 ± 1.69	971.50 ± 96.87	0.60 ± 0.10	−38.80 ± 0.56	35.47 ± 3.78
DCN-loaded bilosomes	–	–	100.00 ± 0.00	301.65 ± 17.32	0.39 ± 0.01	−40.15 ± 3.32	7.77 ± 0.92
(B) E1 (optimal elastosomes)
Observed values			96.25	506.35	0.46	−38.65	12.74
Predicted values			97.20	498.73	0.54	−39.34	14.33

EE%: entrapment efficiency percentage; PS: particle size; PDI: polydispersity index; ZP: zeta potential; DI: deformability index. All the prepared vesicles contained equal amounts of DCN, Span 60, STC, and CH.

^a Data presented as mean ± SD (n = 3).

Figure 2. The release profiles of DCN from the prepared eight elastosomal formulations (A). The size distribution curve (B), transmission electron micrograph (C) of E1 and DSC thermograms of (i) DCN, (ii) CH, (iii) Span 60, (iv) STC, (v) Brij S2, (vi) physical mixture of DCN with elastosomal components and (vii) E1 (D).

Figure 3. Ex-vivo permeation profiles (A), in-vivo skin deposition plot (B) of DCN from E1, DCN-loaded bilosomes and DCN suspension after topical application (*p < .05). Photomicrographs showing histopathological sections (stained using hematoxylin and eosin) of normal untreated rat skin (group I) and rat skin treated with E1 (group II) (C). (i)–(iii) denote the magnification power of 16× to illustrate all skin layers, 40× to identify the epidermis and dermis, and 40× to identify the subcutaneous tissue and muscles, respectively. Abbreviations: epidermis (p), dermis (d), hair follicles (f), subcutaneous tissue (sc), and muscle (m). Mean rhein plasma-concentration time curves (D), release profiles (E), and multiple level C IVIVC between AUC_0→t for 2, 4, and 6 h and percentage DCN released at these time points (b = 0.22; R = 0.976 and b = 0.21; R = 0.984 for E1 and DCN oral suspension, respectively) (F) for E1 and DCN oral suspension.

Table 3. Skin permeability parameters of DCN after topical application of E1, DCN-loaded bilosomes, and drug suspension (A) and pharmacokinetic parameters of E1 in comparison with DCN oral suspension (B).

(A)		Treatment
Skin permeability parameters	E1	DCN-loaded bilosomes	Drug suspension
Total amount of drug permeated per unit area in 24 h (µg/cm^2)^a	1150.92 ± 194.71	1003.50 ± 47.38	59.44 ± 0.50
Jmax (µg/cm^2/h)^a	27.24 ± 4.61	23.75 ± 1.12	1.41 ± 0.01
ER	19.36	16.84	1
(B)
In-vivo pharmacokinetic parameters	E1		DCN oral suspension
Cmax (µg/mL)^b	0.76 ± 0.04		2.24 ± 1.12
Tmax (h)^c	1		1
AUC0→24 (µg h/mL)^b	9.26 ± 3.02		9.95 ± 1.04
AUC0→∞ (µg h/mL)^b	20.65 ± 16.40		15.49 ± 10.04

J_max: flux; ER: enhancement ratio.

^a Data presented as mean ± SD (n = 3).

^b Data presented as mean ± SD (n = 6).

^c Data presented as median.